cJSON.c

/*
  Copyright (c) 2009-2017 Dave Gamble and cJSON contributors

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
*/

/* cJSON */
/* JSON parser in C. */

// 禁用MSVC中关于旧C89函数的警告
#if !defined(_CRT_SECURE_NO_DEPRECATE) && defined(_MSC_VER)
    #define _CRT_SECURE_NO_DEPRECATE
#endif

#ifdef __GNUC__
    #pragma GCC visibility push(default)
#endif

#if defined(_MSC_VER)
    #pragma warning (push)
    // 禁用对系统头文件中单行注释的警告
    #pragma warning (disable : 4001)
#endif

#include <string.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <limits.h>
#include <ctype.h>
#include <float.h>

// locale.h 头文件定义了特定地域的设置
#ifdef ENABLE_LOCALES
    #include <locale.h>
#endif

#if defined(_MSC_VER)
    #pragma warning (pop)
#endif

#ifdef __GNUC__
    #pragma GCC visibility pop
#endif

#include "cJSON.h"

// 自定义定义布尔类型
#ifdef true
    // #undef标识符用来将前面定义的宏标识符取消定义
    #undef true
#endif
#define true ((cJSON_bool)1)
#ifdef false
    #undef false
#endif
#define false ((cJSON_bool)0)

// 为ANSI C定义isnan和isinf，如果在C99或更高版本中，isnan和isinf已在math.h中定义
#ifndef isinf
    #define isinf(d) (isnan((d - d)) && !isnan(d))
#endif
#ifndef isnan
    #define isnan(d) (d != d)
#endif

// 定义NAN
#ifndef NAN
    #ifdef _WIN32
        #define NAN sqrt(-1.0)
    #else
        #define NAN 0.0/0.0
    #endif
#endif

// 报错信息结构体
typedef struct {
    const unsigned char *json;
    size_t position;
} error;
// 默认error信息
static error global_error = { NULL, 0 };
// 返回error信息字符串
CJSON_PUBLIC(const char *) cJSON_GetErrorPtr(void)
{
    return (const char*) (global_error.json + global_error.position);
}

// 获取cJSON节点value
CJSON_PUBLIC(char *) cJSON_GetStringValue(const cJSON * const item)
{
    if (!cJSON_IsString(item))
    {
        return NULL;
    }

    return item->valuestring;
}
CJSON_PUBLIC(double) cJSON_GetNumberValue(const cJSON * const item)
{
    if (!cJSON_IsNumber(item))
    {
        return (double) NAN;
    }

    return item->valuedouble;
}

// 这是一种版本控制保护措施，可防止粘贴复制程序使用不兼容的C和头文件
#if (CJSON_VERSION_MAJOR != 1) || (CJSON_VERSION_MINOR != 7) || (CJSON_VERSION_PATCH != 15)
    #error cJSON.h and cJSON.c have different versions. Make sure that both have the same.
#endif
// 获取版本信息
CJSON_PUBLIC(const char*) cJSON_Version(void)
{
    static char version[15];
    sprintf(version, "%i.%i.%i", CJSON_VERSION_MAJOR, CJSON_VERSION_MINOR, CJSON_VERSION_PATCH);

    return version;
}

// 
typedef struct internal_hooks
{
    void *(CJSON_CDECL *allocate)(size_t size);
    void (CJSON_CDECL *deallocate)(void *pointer);
    void *(CJSON_CDECL *reallocate)(void *pointer, size_t size);
} internal_hooks;
// 防止MSVC编译器C2322错误，详细见https://learn.microsoft.com/zh-cn/cpp/error-messages/compiler-errors-1/compiler-error-c2322?view=msvc-170
#if defined(_MSC_VER)
    static void * CJSON_CDECL internal_malloc(size_t size)
    {
        return malloc(size);
    }
    static void CJSON_CDECL internal_free(void *pointer)
    {
        free(pointer);
    }
    static void * CJSON_CDECL internal_realloc(void *pointer, size_t size)
    {
        return realloc(pointer, size);
    }
#else
    #define internal_malloc malloc
    #define internal_free free
    #define internal_realloc realloc
#endif
static internal_hooks global_hooks = { internal_malloc, internal_free, internal_realloc };

// 在编译时解析的字符字面量的字符串
#define static_strlen(string_literal) (sizeof(string_literal) - sizeof(""))
// 字符串比较函数，不区分大小写比较， 但是两个NULL指针不相等
static int case_insensitive_strcmp(const unsigned char *string1, const unsigned char *string2)
{
    if ((string1 == NULL) || (string2 == NULL))
    {
        return 1;
    }

    if (string1 == string2)
    {
        return 0;
    }

    for(; tolower(*string1) == tolower(*string2); (void)string1++, string2++)
    {
        if (*string1 == '\0')
        {
            return 0;
        }
    }

    return tolower(*string1) - tolower(*string2);
}
// 字符串copy函数，返回一个新的存储位置
static unsigned char* cJSON_strdup(const unsigned char* string, const internal_hooks * const hooks)
{
    size_t length = 0;
    unsigned char *copy = NULL;

    if (string == NULL)
    {
        return NULL;
    }

    length = strlen((const char*)string) + sizeof("");
    copy = (unsigned char*)hooks->allocate(length);
    if (copy == NULL)
    {
        return NULL;
    }
    // 内存拷贝函数,从源内存地址的起始位置开始拷贝length个字节到目标内存地址中
    memcpy(copy, string, length);

    return copy;
}

// hook初始化，内存申请和释放接口
CJSON_PUBLIC(void) cJSON_InitHooks(cJSON_Hooks* hooks)
{
    if (hooks == NULL)
    {
        /* Reset hooks */
        global_hooks.allocate = malloc;
        global_hooks.deallocate = free;
        global_hooks.reallocate = realloc;
        return;
    }

    global_hooks.allocate = malloc;
    if (hooks->malloc_fn != NULL)
    {
        global_hooks.allocate = hooks->malloc_fn;
    }

    global_hooks.deallocate = free;
    if (hooks->free_fn != NULL)
    {
        global_hooks.deallocate = hooks->free_fn;
    }

    /* use realloc only if both free and malloc are used */
    global_hooks.reallocate = NULL;
    if ((global_hooks.allocate == malloc) && (global_hooks.deallocate == free))
    {
        global_hooks.reallocate = realloc;
    }
}

// 节点初始顶层方法，用于申请内存空间
static cJSON *cJSON_New_Item(const internal_hooks * const hooks)
{
    // cJSON* node = (cJSON*)malloc(sizeof(cJSON));
    cJSON* node = (cJSON*)hooks->allocate(sizeof(cJSON));
    if (node)
    {
        //memset是计算机中C/C++语言初始化函数。作用是将某一块内存中的内容全部设置为指定的值
        //这个函数通常为新申请的内存做初始化工作。 原型：void *memset(void *s, int ch, size_t n);
        memset(node, '\0', sizeof(cJSON));
    }
    return node;
}

// 删除节点：标记同组后继节点，递归删除子节点，删除节点，删除后继节点
CJSON_PUBLIC(void) cJSON_Delete(cJSON *item)
{
    cJSON *next = NULL;
    while (item != NULL)
    {
        next = item->next;
        // cJSON_IsReference和cJSON_StringIsConst类型的成员都不删除
        if (!(item->type & cJSON_IsReference) && (item->child != NULL))
        {
            cJSON_Delete(item->child);
        }
        if (!(item->type & cJSON_IsReference) && (item->valuestring != NULL))
        {
            global_hooks.deallocate(item->valuestring);
        }
        if (!(item->type & cJSON_StringIsConst) && (item->string != NULL))
        {
            global_hooks.deallocate(item->string);
        }
        // 删除节点，遍历同组后继节点
        global_hooks.deallocate(item);
        item = next;
    }
}

// 获取当前语言环境的小数点字符
static unsigned char get_decimal_point(void)
{
    #ifdef ENABLE_LOCALES
        struct lconv *lconv = localeconv();
        return (unsigned char) lconv->decimal_point[0];
    #else
        return '.';
    #endif
}

// 反序列化buffer
typedef struct
{
    const unsigned char *content;
    size_t length;
    size_t offset;
    // 在当前偏移量处的嵌套深度(在数组/对象中)。
    size_t depth;
    internal_hooks hooks;
} parse_buffer;

// 检查给定的size是否在缓存区内(从1开始，所以是小于等于)
#define can_read(buffer, size) ((buffer != NULL) && (((buffer)->offset + size) <= (buffer)->length))
// 检查是否可以在给定索引处访问缓冲区(从0开始，所以是小于)
#define can_access_at_index(buffer, index) ((buffer != NULL) && (((buffer)->offset + index) < (buffer)->length))
#define cannot_access_at_index(buffer, index) (!can_access_at_index(buffer, index))
// 获取指向缓冲区最新位置的指针
#define buffer_at_offset(buffer) ((buffer)->content + (buffer)->offset)

// 解析输入文本以生成一个数字，并将结果填充到item中
static cJSON_bool parse_number(cJSON * const item, parse_buffer * const input_buffer)
{
    double number = 0;
    unsigned char *after_end = NULL;
    unsigned char number_c_string[64];
    unsigned char decimal_point = get_decimal_point();
    size_t i = 0;

    if ((input_buffer == NULL) || (input_buffer->content == NULL))
    {
        return false;
    }

    // 将数字复制到临时缓冲区
    for (i = 0; (i < (sizeof(number_c_string) - 1)) && can_access_at_index(input_buffer, i); i++)
    {
        switch (buffer_at_offset(input_buffer)[i])
        {
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
            case '+':
            case '-':
            case 'e':
            case 'E':
                number_c_string[i] = buffer_at_offset(input_buffer)[i];
                break;
            case '.':
                // 替换'.'带有当前语言环境的小数点(对于strtod)
                number_c_string[i] = decimal_point;
                break;
            default:
                // 处理'\0'不一定用于标记输入结束的问题
                goto loop_end;
        }
    }
loop_end:
    number_c_string[i] = '\0';
    // 将字符串转换为一个浮点数（类型为 double 型）
    number = strtod((const char*)number_c_string, (char**)&after_end);
    // after_end指向解析字符串中截至位置的地址，如果与初始地址相等，则表示解析错误
    if (number_c_string == after_end)
    {
        return false;
    }

    item->valuedouble = number;

    // 溢出处理
    if (number >= INT_MAX)
    {
        item->valueint = INT_MAX;
    }
    else if (number <= (double)INT_MIN)
    {
        item->valueint = INT_MIN;
    }
    else
    {
        item->valueint = (int)number;
    }

    item->type = cJSON_Number;
    // 通过after_end计算解析后，带解析的JSON字符串偏移的位置
    input_buffer->offset += (size_t)(after_end - number_c_string);
    return true;
}

// 新的设置number的函数，作者表示：don't ask me 
CJSON_PUBLIC(double) cJSON_SetNumberHelper(cJSON *object, double number)
{
    if (number >= INT_MAX)
    {
        object->valueint = INT_MAX;
    }
    else if (number <= (double)INT_MIN)
    {
        object->valueint = INT_MIN;
    }
    else
    {
        object->valueint = (int)number;
    }

    return object->valuedouble = number;
}
// 设置字符串value
CJSON_PUBLIC(char*) cJSON_SetValuestring(cJSON *object, const char *valuestring)
{
    char *copy = NULL;
    // 如果对象的类型不是cJSON_String或cJSON_IsReference，则不应该设置valuestring
    if (!(object->type & cJSON_String) || (object->type & cJSON_IsReference))
    {
        return NULL;
    }
    if (strlen(valuestring) <= strlen(object->valuestring))
    {
        strcpy(object->valuestring, valuestring);
        return object->valuestring;
    }
    copy = (char*) cJSON_strdup((const unsigned char*)valuestring, &global_hooks);
    if (copy == NULL)
    {
        return NULL;
    }
    if (object->valuestring != NULL)
    {
        cJSON_free(object->valuestring);
    }
    object->valuestring = copy;

    return copy;
}

// 打印JSON字符串buffer
typedef struct
{
    unsigned char *buffer;
    size_t length;
    size_t offset;
    // JSON节点深度
    size_t depth;
    cJSON_bool noalloc;
    // JSON字符串是否格式化（是否回车缩进调整这些）
    cJSON_bool format;
    internal_hooks hooks;
} printbuffer;

// 确保p所指向的缓冲区中能够提供needed大小的缓冲给打印功能使用
static unsigned char* ensure(printbuffer * const p, size_t needed)
{
    unsigned char *newbuffer = NULL;
    size_t newsize = 0;

    if ((p == NULL) || (p->buffer == NULL))
    {
        return NULL;
    }
    // 偏移量超过最大空间
    if ((p->length > 0) && (p->offset >= p->length))
    {    
        return NULL;
    }
    // 不支持大于INT_MAX的大小
    if (needed > INT_MAX)
    {
        return NULL;
    }

    needed += p->offset + 1;
    if (needed <= p->length)
    {
        return p->buffer + p->offset;
    }

    if (p->noalloc) {
        return NULL;
    }

    // 计算新的buffer大小
    if (needed > (INT_MAX / 2))
    {
        if (needed <= INT_MAX)
        {
            newsize = INT_MAX;
        }
        else
        {
            return NULL;
        }
    }
    else
    {
        newsize = needed * 2;
    }

    if (p->hooks.reallocate != NULL)
    {
        // 使用realloc重新分配内存
        newbuffer = (unsigned char*)p->hooks.reallocate(p->buffer, newsize);
        if (newbuffer == NULL)
        {
            p->hooks.deallocate(p->buffer);
            p->length = 0;
            p->buffer = NULL;
            return NULL;
        }
    }
    else
    {
        // 否则手动重新分配
        newbuffer = (unsigned char*)p->hooks.allocate(newsize);
        if (!newbuffer)
        {
            p->hooks.deallocate(p->buffer);
            p->length = 0;
            p->buffer = NULL;
            return NULL;
        }
        memcpy(newbuffer, p->buffer, p->offset + 1);
        p->hooks.deallocate(p->buffer);
    }
    p->length = newsize;
    p->buffer = newbuffer;
    return newbuffer + p->offset;
}

// 在printbuffer中计算字符串的新长度并更新内存偏移量
static void update_offset(printbuffer * const buffer)
{
    const unsigned char *buffer_pointer = NULL;
    if ((buffer == NULL) || (buffer->buffer == NULL))
    {
        return;
    }
    buffer_pointer = buffer->buffer + buffer->offset;

    buffer->offset += strlen((const char*)buffer_pointer);
}

// 浮点变量的安全比较
static cJSON_bool compare_double(double a, double b)
{
    double maxVal = fabs(a) > fabs(b) ? fabs(a) : fabs(b);
    return (fabs(a - b) <= maxVal * DBL_EPSILON);
}

// 解析4位十六进制数
static unsigned parse_hex4(const unsigned char * const input)
{
    unsigned int h = 0;
    size_t i = 0;

    for (i = 0; i < 4; i++)
    {
        // 解析数字
        if ((input[i] >= '0') && (input[i] <= '9'))
        {
            h += (unsigned int) input[i] - '0';
        }
        else if ((input[i] >= 'A') && (input[i] <= 'F'))
        {
            h += (unsigned int) 10 + input[i] - 'A';
        }
        else if ((input[i] >= 'a') && (input[i] <= 'f'))
        {
            h += (unsigned int) 10 + input[i] - 'a';
        }
        else
        {
            // 遇到非法数字
            return 0;
        }
        // 移位，流出位置（因为是16进制，所以移4位）
        if (i < 3)
        {
            h = h << 4;
        }
    }

    return h;
}
// 将UTF-16字面值转换为UTF-8 字面量可以是一个或两个形式为\uXXXX的序列
static unsigned char utf16_literal_to_utf8(const unsigned char * const input_pointer, const unsigned char * const input_end, unsigned char **output_pointer)
{
    long unsigned int codepoint = 0;
    unsigned int first_code = 0;
    const unsigned char *first_sequence = input_pointer;
    unsigned char utf8_length = 0;
    unsigned char utf8_position = 0;
    unsigned char sequence_length = 0;
    unsigned char first_byte_mark = 0;

    if ((input_end - first_sequence) < 6)
    {
        /* input ends unexpectedly */
        goto fail;
    }

    /* get the first utf16 sequence */
    first_code = parse_hex4(first_sequence + 2);

    /* check that the code is valid */
    if (((first_code >= 0xDC00) && (first_code <= 0xDFFF)))
    {
        goto fail;
    }

    /* UTF16 surrogate pair */
    if ((first_code >= 0xD800) && (first_code <= 0xDBFF))
    {
        const unsigned char *second_sequence = first_sequence + 6;
        unsigned int second_code = 0;
        sequence_length = 12; /* \uXXXX\uXXXX */

        if ((input_end - second_sequence) < 6)
        {
            /* input ends unexpectedly */
            goto fail;
        }

        if ((second_sequence[0] != '\\') || (second_sequence[1] != 'u'))
        {
            /* missing second half of the surrogate pair */
            goto fail;
        }

        /* get the second utf16 sequence */
        second_code = parse_hex4(second_sequence + 2);
        /* check that the code is valid */
        if ((second_code < 0xDC00) || (second_code > 0xDFFF))
        {
            /* invalid second half of the surrogate pair */
            goto fail;
        }


        /* calculate the unicode codepoint from the surrogate pair */
        codepoint = 0x10000 + (((first_code & 0x3FF) << 10) | (second_code & 0x3FF));
    }
    else
    {
        sequence_length = 6; /* \uXXXX */
        codepoint = first_code;
    }

    /* encode as UTF-8
     * takes at maximum 4 bytes to encode:
     * 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
    if (codepoint < 0x80)
    {
        /* normal ascii, encoding 0xxxxxxx */
        utf8_length = 1;
    }
    else if (codepoint < 0x800)
    {
        /* two bytes, encoding 110xxxxx 10xxxxxx */
        utf8_length = 2;
        first_byte_mark = 0xC0; /* 11000000 */
    }
    else if (codepoint < 0x10000)
    {
        /* three bytes, encoding 1110xxxx 10xxxxxx 10xxxxxx */
        utf8_length = 3;
        first_byte_mark = 0xE0; /* 11100000 */
    }
    else if (codepoint <= 0x10FFFF)
    {
        /* four bytes, encoding 1110xxxx 10xxxxxx 10xxxxxx 10xxxxxx */
        utf8_length = 4;
        first_byte_mark = 0xF0; /* 11110000 */
    }
    else
    {
        /* invalid unicode codepoint */
        goto fail;
    }

    /* encode as utf8 */
    for (utf8_position = (unsigned char)(utf8_length - 1); utf8_position > 0; utf8_position--)
    {
        /* 10xxxxxx */
        (*output_pointer)[utf8_position] = (unsigned char)((codepoint | 0x80) & 0xBF);
        codepoint >>= 6;
    }
    /* encode first byte */
    if (utf8_length > 1)
    {
        (*output_pointer)[0] = (unsigned char)((codepoint | first_byte_mark) & 0xFF);
    }
    else
    {
        (*output_pointer)[0] = (unsigned char)(codepoint & 0x7F);
    }

    *output_pointer += utf8_length;

    return sequence_length;

fail:
    return 0;
}

// 去除buffer中的其他字符（ASCII码小于等于32的字符）
static parse_buffer *buffer_skip_whitespace(parse_buffer * const buffer)
{
    if ((buffer == NULL) || (buffer->content == NULL))
    {
        return NULL;
    }

    if (cannot_access_at_index(buffer, 0))
    {
        return buffer;
    }

    while (can_access_at_index(buffer, 0) && (buffer_at_offset(buffer)[0] <= 32))
    {
       buffer->offset++;
    }

    if (buffer->offset == buffer->length)
    {
        buffer->offset--;
    }

    return buffer;
}
// 去除UTP-8 BOM头，BOM头是用于标记UTF-8编码的
static parse_buffer *skip_utf8_bom(parse_buffer * const buffer)
{
    if ((buffer == NULL) || (buffer->content == NULL) || (buffer->offset != 0))
    {
        return NULL;
    }

    if (can_access_at_index(buffer, 4) && (strncmp((const char*)buffer_at_offset(buffer), "\xEF\xBB\xBF", 3) == 0))
    {
        buffer->offset += 3;
    }

    return buffer;
}

// 大小比较器
#define cjson_min(a, b) (((a) < (b)) ? (a) : (b))

// 将输入的文本解析为非转义的c的字符串
static cJSON_bool print_string_ptr(const unsigned char * const input, printbuffer * const output_buffer)
{
    const unsigned char *input_pointer = NULL;
    unsigned char *output = NULL;
    unsigned char *output_pointer = NULL;
    size_t output_length = 0;
    // 转义所需的附加字符数
    size_t escape_characters = 0;

    if (output_buffer == NULL)
    {
        return false;
    }

    // 空字符串
    if (input == NULL)
    {
        output = ensure(output_buffer, sizeof("\"\""));
        if (output == NULL)
        {
            return false;
        }
        strcpy((char*)output, "\"\"");

        return true;
    }

    // 计算转义所需的附加字符数
    for (input_pointer = input; *input_pointer; input_pointer++)
    {
        switch (*input_pointer)
        {
            case '\"':
            case '\\':
            case '\b':
            case '\f':
            case '\n':
            case '\r':
            case '\t':
                /* one character escape sequence */
                escape_characters++;
                break;
            default:
                if (*input_pointer < 32)
                {
                    /* UTF-16 escape sequence uXXXX */
                    escape_characters += 5;
                }
                break;
        }
    }
    output_length = (size_t)(input_pointer - input) + escape_characters;

    output = ensure(output_buffer, output_length + sizeof("\"\""));
    if (output == NULL)
    {
        return false;
    }

    // 无转义字符
    if (escape_characters == 0)
    {
        output[0] = '\"';
        memcpy(output + 1, input, output_length);
        output[output_length + 1] = '\"';
        output[output_length + 2] = '\0';

        return true;
    }

    // 存在转义字符
    output[0] = '\"';
    output_pointer = output + 1;
    // 拷贝字符串
    for (input_pointer = input; *input_pointer != '\0'; (void)input_pointer++, output_pointer++)
    {
        if ((*input_pointer > 31) && (*input_pointer != '\"') && (*input_pointer != '\\'))
        {
            // 正常字符
            *output_pointer = *input_pointer;
        }
        else
        {
            // 需转义字符
            *output_pointer++ = '\\';
            switch (*input_pointer)
            {
                case '\\':
                    *output_pointer = '\\';
                    break;
                case '\"':
                    *output_pointer = '\"';
                    break;
                case '\b':
                    *output_pointer = 'b';
                    break;
                case '\f':
                    *output_pointer = 'f';
                    break;
                case '\n':
                    *output_pointer = 'n';
                    break;
                case '\r':
                    *output_pointer = 'r';
                    break;
                case '\t':
                    *output_pointer = 't';
                    break;
                default:
                    // 转义并作为unicode码点打印
                    sprintf((char*)output_pointer, "u%04x", *input_pointer);
                    output_pointer += 4;
                    break;
            }
        }
    }
    output[output_length + 1] = '\"';
    output[output_length + 2] = '\0';

    return true;
}
// 将item中的valuestring打印到分配的内存中或者是缓存p中
static cJSON_bool print_string(const cJSON * const item, printbuffer * const p)
{
    return print_string_ptr((unsigned char*)item->valuestring, p);
}
// 序列化数字类型的cJSON节点
static cJSON_bool print_number(const cJSON * const item, printbuffer * const output_buffer)
{
    unsigned char *output_pointer = NULL;
    double d = item->valuedouble;
    int length = 0;
    size_t i = 0;
    // 将数字打印到的临时缓冲区
    unsigned char number_buffer[26] = {0};
    unsigned char decimal_point = get_decimal_point();
    double test = 0.0;

    if (output_buffer == NULL)
    {
        return false;
    }

    if (isnan(d) || isinf(d))
    {
        // 数字不合法
        length = sprintf((char*)number_buffer, "null");
    }
	else if(d == (double)item->valueint)
	{
        // 整数
		length = sprintf((char*)number_buffer, "%d", item->valueint);
	}
    else
    {
        // 浮点数
        // 精度为15位小数，以避免不重要的非零数字
        length = sprintf((char*)number_buffer, "%1.15g", d);

        // 检查是否能还原数字
        if ((sscanf((char*)number_buffer, "%lg", &test) != 1) || !compare_double((double)test, d))
        {
            // 不能还原表示精度不够
            length = sprintf((char*)number_buffer, "%1.17g", d);
        }
    }
    // sprint失败或缓冲区溢出
    if ((length < 0) || (length > (int)(sizeof(number_buffer) - 1)))
    {
        return false;
    }
    // 确保缓冲区中有足够的空间
    output_pointer = ensure(output_buffer, (size_t)length + sizeof(""));
    if (output_pointer == NULL)
    {
        return false;
    }

    // 将打印的数字复制到输出并替换区域设置，替换小数点'.'
    for (i = 0; i < ((size_t)length); i++)
    {
        if (number_buffer[i] == decimal_point)
        {
            output_pointer[i] = '.';
            continue;
        }

        output_pointer[i] = number_buffer[i];
    }
    output_pointer[i] = '\0';

    output_buffer->offset += (size_t)length;

    return true;
}

// 静态函数原型声明
static cJSON_bool parse_value(cJSON * const item, parse_buffer * const input_buffer);
static cJSON_bool print_value(const cJSON * const item, printbuffer * const output_buffer);
static cJSON_bool parse_array(cJSON * const item, parse_buffer * const input_buffer);
static cJSON_bool print_array(const cJSON * const item, printbuffer * const output_buffer);
static cJSON_bool parse_object(cJSON * const item, parse_buffer * const input_buffer);
static cJSON_bool print_object(const cJSON * const item, printbuffer * const output_buffer);

// 根据设置解析JSON字符串
CJSON_PUBLIC(cJSON *) cJSON_ParseWithOpts(const char *value, const char **return_parse_end, cJSON_bool require_null_terminated)
{
    size_t buffer_length;

    if (NULL == value)
    {
        return NULL;
    }
    // 为'\0'添加一位索引，方便后续判断是否解析至value字符串最后
    buffer_length = strlen(value) + sizeof("");

    return cJSON_ParseWithLengthOpts(value, buffer_length, return_parse_end, require_null_terminated);
}
// 解析一个对象——创建一个新的根，然后填充。
CJSON_PUBLIC(cJSON *) cJSON_ParseWithLengthOpts(const char *value, size_t buffer_length, const char **return_parse_end, cJSON_bool require_null_terminated)
{
    parse_buffer buffer = { 0, 0, 0, 0, { 0, 0, 0 } };
    cJSON *item = NULL;

    /* reset error position */
    global_error.json = NULL;
    global_error.position = 0;

    if (value == NULL || 0 == buffer_length)
    {
        goto fail;
    }

    buffer.content = (const unsigned char*)value;
    buffer.length = buffer_length;
    buffer.offset = 0;
    buffer.hooks = global_hooks;

    item = cJSON_New_Item(&global_hooks);
    if (item == NULL) 
    {
        goto fail;
    }

    if (!parse_value(item, buffer_skip_whitespace(skip_utf8_bom(&buffer))))
    {
        goto fail;
    }

    // 未解析到字符串最后位置，则说明解析失败
    if (require_null_terminated)
    {
        buffer_skip_whitespace(&buffer);
        if ((buffer.offset >= buffer.length) || buffer_at_offset(&buffer)[0] != '\0')
        {
            goto fail;
        }
    }
    if (return_parse_end)
    {
        *return_parse_end = (const char*)buffer_at_offset(&buffer);
    }

    return item;

fail:
    // 释放新建的节点空间
    if (item != NULL)
    {
        cJSON_Delete(item);
    }
    // 异常信息处理
    if (value != NULL)
    {
        error local_error;
        local_error.json = (const unsigned char*)value;
        local_error.position = 0;

        if (buffer.offset < buffer.length)
        {
            local_error.position = buffer.offset;
        }
        else if (buffer.length > 0)
        {
            local_error.position = buffer.length - 1;
        }

        if (return_parse_end != NULL)
        {
            *return_parse_end = (const char*)local_error.json + local_error.position;
        }

        global_error = local_error;
    }

    return NULL;
}
// 解析JSON字符串的调用入口
CJSON_PUBLIC(cJSON *) cJSON_Parse(const char *value)
{
    return cJSON_ParseWithOpts(value, 0, 0);
}
// 根据长度解析JSON字符串
CJSON_PUBLIC(cJSON *) cJSON_ParseWithLength(const char *value, size_t buffer_length)
{
    return cJSON_ParseWithLengthOpts(value, buffer_length, 0, 0);
}
// 将输入的文本解析为非转义的c的字符串，然后填充到item中，应该保证str是已经去除开头空字符的串
static cJSON_bool parse_string(cJSON * const item, parse_buffer * const input_buffer)
{
    const unsigned char *input_pointer = buffer_at_offset(input_buffer) + 1;
    const unsigned char *input_end = buffer_at_offset(input_buffer) + 1;
    unsigned char *output_pointer = NULL;
    unsigned char *output = NULL;

    // 不用以引号开头，则不是字符串
    if (buffer_at_offset(input_buffer)[0] != '\"')
    {
        goto fail;
    }

    {
        // 计算输出的大致大小(高估)
        size_t allocation_length = 0;
        size_t skipped_bytes = 0;
        while (((size_t)(input_end - input_buffer->content) < input_buffer->length) && (*input_end != '\"'))
        {
            // 转义字符
            if (input_end[0] == '\\')
            {
                // 空间溢出
                if ((size_t)(input_end + 1 - input_buffer->content) >= input_buffer->length)
                {
                    goto fail;
                }
                skipped_bytes++;
                input_end++;
            }
            input_end++;
        }
        // 字符串意外结束
        if (((size_t)(input_end - input_buffer->content) >= input_buffer->length) || (*input_end != '\"'))
        {
            goto fail;
        }

        // 高估需要打印的长度
        allocation_length = (size_t) (input_end - buffer_at_offset(input_buffer)) - skipped_bytes;
        output = (unsigned char*)input_buffer->hooks.allocate(allocation_length + sizeof(""));
        if (output == NULL)
        {
            goto fail; /* allocation failure */
        }
    }

    output_pointer = output;
    // 循环遍历字符串字面值
    while (input_pointer < input_end)
    {
        if (*input_pointer != '\\')
        {
            *output_pointer++ = *input_pointer++;
        }
        // 处理转义字符
        else
        {
            unsigned char sequence_length = 2;
            if ((input_end - input_pointer) < 1)
            {
                goto fail;
            }

            switch (input_pointer[1])
            {
                case 'b':
                    *output_pointer++ = '\b';
                    break;
                case 'f':
                    *output_pointer++ = '\f';
                    break;
                case 'n':
                    *output_pointer++ = '\n';
                    break;
                case 'r':
                    *output_pointer++ = '\r';
                    break;
                case 't':
                    *output_pointer++ = '\t';
                    break;
                case '\"':
                case '\\':
                case '/':
                    *output_pointer++ = input_pointer[1];
                    break;

                /* UTF-16 literal */
                case 'u':
                    sequence_length = utf16_literal_to_utf8(input_pointer, input_end, &output_pointer);
                    if (sequence_length == 0)
                    {
                        /* failed to convert UTF16-literal to UTF-8 */
                        goto fail;
                    }
                    break;

                default:
                    goto fail;
            }
            input_pointer += sequence_length;
        }
    }

    *output_pointer = '\0';

    item->type = cJSON_String;
    item->valuestring = (char*)output;

    input_buffer->offset = (size_t) (input_end - input_buffer->content);
    input_buffer->offset++;

    return true;

fail:
    if (output != NULL)
    {
        input_buffer->hooks.deallocate(output);
    }

    if (input_pointer != NULL)
    {
        input_buffer->offset = (size_t)(input_pointer - input_buffer->content);
    }

    return false;
}
// JSON字符串解析入口函数
static cJSON_bool parse_value(cJSON * const item, parse_buffer * const input_buffer)
{
    if ((input_buffer == NULL) || (input_buffer->content == NULL))
    {
        return false; /* no input */
    }

    // 解析不同类型的值
    // int strncmp(const char *str1, const char *str2, size_t n) 把 str1 和 str2 进行比较，最多比较前 n 个字节
    /* null */
    if (can_read(input_buffer, 4) && (strncmp((const char*)buffer_at_offset(input_buffer), "null", 4) == 0))
    {
        item->type = cJSON_NULL;
        input_buffer->offset += 4;
        return true;
    }
    /* false */
    if (can_read(input_buffer, 5) && (strncmp((const char*)buffer_at_offset(input_buffer), "false", 5) == 0))
    {
        item->type = cJSON_False;
        input_buffer->offset += 5;
        return true;
    }
    /* true */
    if (can_read(input_buffer, 4) && (strncmp((const char*)buffer_at_offset(input_buffer), "true", 4) == 0))
    {
        item->type = cJSON_True;
        item->valueint = 1;
        input_buffer->offset += 4;
        return true;
    }
    /* string */
    if (can_access_at_index(input_buffer, 0) && (buffer_at_offset(input_buffer)[0] == '\"'))
    {
        return parse_string(item, input_buffer);
    }
    /* number */
    if (can_access_at_index(input_buffer, 0) && ((buffer_at_offset(input_buffer)[0] == '-') || ((buffer_at_offset(input_buffer)[0] >= '0') && (buffer_at_offset(input_buffer)[0] <= '9'))))
    {
        return parse_number(item, input_buffer);
    }
    /* array */
    if (can_access_at_index(input_buffer, 0) && (buffer_at_offset(input_buffer)[0] == '['))
    {
        return parse_array(item, input_buffer);
    }
    /* object */
    if (can_access_at_index(input_buffer, 0) && (buffer_at_offset(input_buffer)[0] == '{'))
    {
        return parse_object(item, input_buffer);
    }

    return false;
}
// parse_array和parse_object非常类似，因为采用了相同的数据结构
static cJSON_bool parse_array(cJSON * const item, parse_buffer * const input_buffer)
{
    cJSON *head = NULL; /* head of the linked list */
    cJSON *current_item = NULL;

    if (input_buffer->depth >= CJSON_NESTING_LIMIT)
    {
        return false; /* to deeply nested */
    }
    input_buffer->depth++;

    if (buffer_at_offset(input_buffer)[0] != '[')
    {
        /* not an array */
        goto fail;
    }

    input_buffer->offset++;
    buffer_skip_whitespace(input_buffer);
    if (can_access_at_index(input_buffer, 0) && (buffer_at_offset(input_buffer)[0] == ']'))
    {
        /* empty array */
        goto success;
    }

    /* check if we skipped to the end of the buffer */
    if (cannot_access_at_index(input_buffer, 0))
    {
        input_buffer->offset--;
        goto fail;
    }

    /* step back to character in front of the first element */
    input_buffer->offset--;
    /* loop through the comma separated array elements */
    do
    {
        /* allocate next item */
        cJSON *new_item = cJSON_New_Item(&(input_buffer->hooks));
        if (new_item == NULL)
        {
            goto fail; /* allocation failure */
        }

        /* attach next item to list */
        if (head == NULL)
        {
            /* start the linked list */
            current_item = head = new_item;
        }
        else
        {
            /* add to the end and advance */
            current_item->next = new_item;
            new_item->prev = current_item;
            current_item = new_item;
        }

        /* parse next value */
        input_buffer->offset++;
        buffer_skip_whitespace(input_buffer);
        if (!parse_value(current_item, input_buffer))
        {
            goto fail; /* failed to parse value */
        }
        buffer_skip_whitespace(input_buffer);
    }
    while (can_access_at_index(input_buffer, 0) && (buffer_at_offset(input_buffer)[0] == ','));

    if (cannot_access_at_index(input_buffer, 0) || buffer_at_offset(input_buffer)[0] != ']')
    {
        goto fail; /* expected end of array */
    }

success:
    input_buffer->depth--;

    if (head != NULL) {
        head->prev = current_item;
    }

    item->type = cJSON_Array;
    item->child = head;

    input_buffer->offset++;

    return true;

fail:
    if (head != NULL)
    {
        cJSON_Delete(head);
    }

    return false;
}
// 解析JSON字符串中对象类型
static cJSON_bool parse_object(cJSON * const item, parse_buffer * const input_buffer)
{
    cJSON *head = NULL; /* linked list head */
    cJSON *current_item = NULL;

    // 嵌套深度太深（超过1000层）
    if (input_buffer->depth >= CJSON_NESTING_LIMIT)
    {
        return false;
    }
    input_buffer->depth++;
    // 错误对象
    if (cannot_access_at_index(input_buffer, 0) || (buffer_at_offset(input_buffer)[0] != '{'))
    {
        goto fail;
    }

    input_buffer->offset++;
    buffer_skip_whitespace(input_buffer);
    // 空对象
    if (can_access_at_index(input_buffer, 0) && (buffer_at_offset(input_buffer)[0] == '}'))
    {
        goto success;
    }

    /* 检查是否跳到缓冲区的末尾 */
    if (cannot_access_at_index(input_buffer, 0))
    {
        input_buffer->offset--;
        goto fail;
    }

    // 退回到第一个元素前面的字符
    input_buffer->offset--;
    // 循环遍历逗号分隔的数组元素
    do
    {
        /* allocate next item */
        cJSON *new_item = cJSON_New_Item(&(input_buffer->hooks));
        if (new_item == NULL)
        {
            goto fail; /* allocation failure */
        }

        /* attach next item to list */
        if (head == NULL)
        {
            /* start the linked list */
            current_item = head = new_item;
        }
        else
        {
            /* add to the end and advance */
            current_item->next = new_item;
            new_item->prev = current_item;
            current_item = new_item;
        }
        // 借助parse_string去提取key值，然后交换valuestring和string值
        input_buffer->offset++;
        buffer_skip_whitespace(input_buffer);
        if (!parse_string(current_item, input_buffer))
        {
            goto fail; /* failed to parse name */
        }
        buffer_skip_whitespace(input_buffer);

        // 交换valuestring和string，因为是在解析key
        current_item->string = current_item->valuestring;
        current_item->valuestring = NULL;

        if (cannot_access_at_index(input_buffer, 0) || (buffer_at_offset(input_buffer)[0] != ':'))
        {
            goto fail; /* invalid object */
        }

        // 解析value
        input_buffer->offset++;
        buffer_skip_whitespace(input_buffer);
        if (!parse_value(current_item, input_buffer))
        {
            goto fail; /* failed to parse value */
        }
        buffer_skip_whitespace(input_buffer);
    }
    while (can_access_at_index(input_buffer, 0) && (buffer_at_offset(input_buffer)[0] == ','));

    if (cannot_access_at_index(input_buffer, 0) || (buffer_at_offset(input_buffer)[0] != '}'))
    {
        goto fail; /* expected end of object */
    }

// 成功：退回原深度，链接父子节点，更新buffer内存偏移量
success:
    input_buffer->depth--;

    if (head != NULL) {
        head->prev = current_item;
    }

    item->type = cJSON_Object;
    item->child = head;

    input_buffer->offset++;
    return true;

fail:
    if (head != NULL)
    {
        cJSON_Delete(head);
    }

    return false;
}

// 打印JSON字符串核心函数
static unsigned char *print(const cJSON * const item, cJSON_bool format, const internal_hooks * const hooks)
{
    static const size_t default_buffer_size = 256;
    printbuffer buffer[1];
    unsigned char *printed = NULL;

    memset(buffer, 0, sizeof(buffer));

    /* create buffer */
    buffer->buffer = (unsigned char*) hooks->allocate(default_buffer_size);
    buffer->length = default_buffer_size;
    buffer->format = format;
    buffer->hooks = *hooks;
    if (buffer->buffer == NULL)
    {
        goto fail;
    }

    /* print the value */
    if (!print_value(item, buffer))
    {
        goto fail;
    }
    update_offset(buffer);

    /* check if reallocate is available */
    if (hooks->reallocate != NULL)
    {
        printed = (unsigned char*) hooks->reallocate(buffer->buffer, buffer->offset + 1);
        if (printed == NULL) {
            goto fail;
        }
        buffer->buffer = NULL;
    }
    else /* otherwise copy the JSON over to a new buffer */
    {
        printed = (unsigned char*) hooks->allocate(buffer->offset + 1);
        if (printed == NULL)
        {
            goto fail;
        }
        memcpy(printed, buffer->buffer, cjson_min(buffer->length, buffer->offset + 1));
        printed[buffer->offset] = '\0'; /* just to be sure */

        /* free the buffer */
        hooks->deallocate(buffer->buffer);
    }

    return printed;

fail:
    if (buffer->buffer != NULL)
    {
        hooks->deallocate(buffer->buffer);
    }

    if (printed != NULL)
    {
        hooks->deallocate(printed);
    }

    return NULL;
}
// 格式化打印JSON
CJSON_PUBLIC(char *) cJSON_Print(const cJSON *item)
{
    return (char*)print(item, true, &global_hooks);
}
// 非格式化打印JSON
CJSON_PUBLIC(char *) cJSON_PrintUnformatted(const cJSON *item)
{
    return (char*)print(item, false, &global_hooks);
}
// 打印cJSON到缓存中
CJSON_PUBLIC(char *) cJSON_PrintBuffered(const cJSON *item, int prebuffer, cJSON_bool fmt)
{
    printbuffer p = { 0, 0, 0, 0, 0, 0, { 0, 0, 0 } };

    if (prebuffer < 0)
    {
        return NULL;
    }

    p.buffer = (unsigned char*)global_hooks.allocate((size_t)prebuffer);
    if (!p.buffer)
    {
        return NULL;
    }

    p.length = (size_t)prebuffer;
    p.offset = 0;
    p.noalloc = false;
    p.format = fmt;
    p.hooks = global_hooks;

    if (!print_value(item, &p))
    {
        global_hooks.deallocate(p.buffer);
        return NULL;
    }

    return (char*)p.buffer;
}
CJSON_PUBLIC(cJSON_bool) cJSON_PrintPreallocated(cJSON *item, char *buffer, const int length, const cJSON_bool format)
{
    printbuffer p = { 0, 0, 0, 0, 0, 0, { 0, 0, 0 } };

    if ((length < 0) || (buffer == NULL))
    {
        return false;
    }

    p.buffer = (unsigned char*)buffer;
    p.length = (size_t)length;
    p.offset = 0;
    p.noalloc = true;
    p.format = format;
    p.hooks = global_hooks;

    return print_value(item, &p);
}
// 根据cJSON节点类型分别调用打印函数
static cJSON_bool print_value(const cJSON * const item, printbuffer * const output_buffer)
{
    unsigned char *output = NULL;

    if ((item == NULL) || (output_buffer == NULL))
    {
        return false;
    }

    switch ((item->type) & 0xFF)
    {
        case cJSON_NULL:
            output = ensure(output_buffer, 5);
            if (output == NULL)
            {
                return false;
            }
            strcpy((char*)output, "null");
            return true;

        case cJSON_False:
            output = ensure(output_buffer, 6);
            if (output == NULL)
            {
                return false;
            }
            strcpy((char*)output, "false");
            return true;

        case cJSON_True:
            output = ensure(output_buffer, 5);
            if (output == NULL)
            {
                return false;
            }
            strcpy((char*)output, "true");
            return true;

        case cJSON_Number:
            return print_number(item, output_buffer);

        case cJSON_Raw:
        {
            size_t raw_length = 0;
            if (item->valuestring == NULL)
            {
                return false;
            }

            raw_length = strlen(item->valuestring) + sizeof("");
            output = ensure(output_buffer, raw_length);
            if (output == NULL)
            {
                return false;
            }
            memcpy(output, item->valuestring, raw_length);
            return true;
        }

        case cJSON_String:
            return print_string(item, output_buffer);

        case cJSON_Array:
            return print_array(item, output_buffer);

        case cJSON_Object:
            return print_object(item, output_buffer);

        default:
            return false;
    }
}
// 打印对象类型cJSON节点
static cJSON_bool print_object(const cJSON * const item, printbuffer * const output_buffer)
{
    unsigned char *output_pointer = NULL;
    size_t length = 0;
    cJSON *current_item = item->child;

    if (output_buffer == NULL)
    {
        return false;
    }

    /* Compose the output: */
    length = (size_t) (output_buffer->format ? 2 : 1); /* fmt: {\n */
    output_pointer = ensure(output_buffer, length + 1);
    if (output_pointer == NULL)
    {
        return false;
    }

    *output_pointer++ = '{';
    output_buffer->depth++;
    if (output_buffer->format)
    {
        *output_pointer++ = '\n';
    }
    output_buffer->offset += length;

    while (current_item)
    {
        // Tab缩进格式化
        if (output_buffer->format)
        {
            size_t i;
            output_pointer = ensure(output_buffer, output_buffer->depth);
            if (output_pointer == NULL)
            {
                return false;
            }
            for (i = 0; i < output_buffer->depth; i++)
            {
                *output_pointer++ = '\t';
            }
            output_buffer->offset += output_buffer->depth;
        }

        /* print key */
        if (!print_string_ptr((unsigned char*)current_item->string, output_buffer))
        {
            return false;
        }
        update_offset(output_buffer);

        length = (size_t) (output_buffer->format ? 2 : 1);
        output_pointer = ensure(output_buffer, length);
        if (output_pointer == NULL)
        {
            return false;
        }
        *output_pointer++ = ':';
        if (output_buffer->format)
        {
            *output_pointer++ = '\t';
        }
        output_buffer->offset += length;

        /* print value */
        if (!print_value(current_item, output_buffer))
        {
            return false;
        }
        update_offset(output_buffer);

        /* print comma if not last */
        length = ((size_t)(output_buffer->format ? 1 : 0) + (size_t)(current_item->next ? 1 : 0));
        output_pointer = ensure(output_buffer, length + 1);
        if (output_pointer == NULL)
        {
            return false;
        }
        if (current_item->next)
        {
            *output_pointer++ = ',';
        }

        if (output_buffer->format)
        {
            *output_pointer++ = '\n';
        }
        *output_pointer = '\0';
        output_buffer->offset += length;

        current_item = current_item->next;
    }

    output_pointer = ensure(output_buffer, output_buffer->format ? (output_buffer->depth + 1) : 2);
    if (output_pointer == NULL)
    {
        return false;
    }
    if (output_buffer->format)
    {
        size_t i;
        for (i = 0; i < (output_buffer->depth - 1); i++)
        {
            *output_pointer++ = '\t';
        }
    }
    *output_pointer++ = '}';
    *output_pointer = '\0';
    output_buffer->depth--;

    return true;
}
// 打印数组类型cJSON节点
static cJSON_bool print_array(const cJSON * const item, printbuffer * const output_buffer)
{
    unsigned char *output_pointer = NULL;
    size_t length = 0;
    cJSON *current_element = item->child;

    if (output_buffer == NULL)
    {
        return false;
    }

    // 拼接输出数组。
    output_pointer = ensure(output_buffer, 1);
    if (output_pointer == NULL)
    {
        return false;
    }

    *output_pointer = '[';
    output_buffer->offset++;
    output_buffer->depth++;

    while (current_element != NULL)
    {
        if (!print_value(current_element, output_buffer))
        {
            return false;
        }
        update_offset(output_buffer);
        if (current_element->next)
        {
            length = (size_t) (output_buffer->format ? 2 : 1);
            output_pointer = ensure(output_buffer, length + 1);
            if (output_pointer == NULL)
            {
                return false;
            }
            *output_pointer++ = ',';
            if(output_buffer->format)
            {
                *output_pointer++ = ' ';
            }
            *output_pointer = '\0';
            output_buffer->offset += length;
        }
        current_element = current_element->next;
    }

    output_pointer = ensure(output_buffer, 2);
    if (output_pointer == NULL)
    {
        return false;
    }
    *output_pointer++ = ']';
    *output_pointer = '\0';
    output_buffer->depth--;

    return true;
}

// 获取数组大小
CJSON_PUBLIC(int) cJSON_GetArraySize(const cJSON *array)
{
    cJSON *child = NULL;
    size_t size = 0;

    if (array == NULL)
    {
        return 0;
    }

    child = array->child;

    while(child != NULL)
    {
        size++;
        child = child->next;
    }

    /* FIXME: Can overflow here. Cannot be fixed without breaking the API */

    return (int)size;
}
// 获得节点数组的index位置元素
static cJSON* get_array_item(const cJSON *array, size_t index)
{
    cJSON *current_child = NULL;

    if (array == NULL)
    {
        return NULL;
    }

    current_child = array->child;
    while ((current_child != NULL) && (index > 0))
    {
        index--;
        current_child = current_child->next;
    }

    return current_child;
}
CJSON_PUBLIC(cJSON *) cJSON_GetArrayItem(const cJSON *array, int index)
{
    if (index < 0)
    {
        return NULL;
    }

    return get_array_item(array, (size_t)index);
}

// 获取元素
static cJSON *get_object_item(const cJSON * const object, const char * const name, const cJSON_bool case_sensitive)
{
    cJSON *current_element = NULL;

    if ((object == NULL) || (name == NULL))
    {
        return NULL;
    }

    current_element = object->child;
    if (case_sensitive)
    {
        while ((current_element != NULL) && (current_element->string != NULL) && (strcmp(name, current_element->string) != 0))
        {
            current_element = current_element->next;
        }
    }
    else
    {
        while ((current_element != NULL) && (case_insensitive_strcmp((const unsigned char*)name, (const unsigned char*)(current_element->string)) != 0))
        {
            current_element = current_element->next;
        }
    }

    if ((current_element == NULL) || (current_element->string == NULL)) {
        return NULL;
    }

    return current_element;
}
CJSON_PUBLIC(cJSON *) cJSON_GetObjectItem(const cJSON * const object, const char * const string)
{
    return get_object_item(object, string, false);
}
CJSON_PUBLIC(cJSON *) cJSON_GetObjectItemCaseSensitive(const cJSON * const object, const char * const string)
{
    return get_object_item(object, string, true);
}

// 判断是否存在指定key
CJSON_PUBLIC(cJSON_bool) cJSON_HasObjectItem(const cJSON *object, const char *string)
{
    return cJSON_GetObjectItem(object, string) ? 1 : 0;
}

// 链接插入节点辅助函数
static void suffix_object(cJSON *prev, cJSON *item)
{
    prev->next = item;
    item->prev = prev;
}

// 创建item节点的引用节点
static cJSON *create_reference(const cJSON *item, const internal_hooks * const hooks)
{
    cJSON *reference = NULL;
    if (item == NULL)
    {
        return NULL;
    }

    reference = cJSON_New_Item(hooks);
    if (reference == NULL)
    {
        return NULL;
    }

    memcpy(reference, item, sizeof(cJSON));
    reference->string = NULL;
    reference->type |= cJSON_IsReference;
    reference->next = reference->prev = NULL;
    return reference;
}

// 用于记录当前的诊断状态
#if defined(__clang__) || (defined(__GNUC__)  && ((__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ > 5))))
    #pragma GCC diagnostic push
#endif
// 用于屏蔽局部代码的警告
#ifdef __GNUC__
    #pragma GCC diagnostic ignored "-Wcast-qual"
#endif

// 转换const的辅助函数
static void* cast_away_const(const void* string)
{
    return (void*)string;
}

// 用于恢复诊断状态，显示警告信息
#if defined(__clang__) || (defined(__GNUC__)  && ((__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ > 5))))
    #pragma GCC diagnostic pop
#endif

// 以常量string为键向对象添加cJSON节点
static cJSON_bool add_item_to_array(cJSON *array, cJSON *item)
{
    cJSON *child = NULL;

    if ((item == NULL) || (array == NULL) || (array == item))
    {
        return false;
    }

    // 插入位置为子节点链表处
    child = array->child;
    /*
     * To find the last item in array quickly, we use prev in array
        无头结点插入
     */
    if (child == NULL)
    {
        /* list is empty, start new one */
        array->child = item;
        item->prev = item;
        item->next = NULL;
    }
    else
    {
        /* append to the end  
            有头结点追加（尾插法）
         */
        if (child->prev)
        {
            suffix_object(child->prev, item);
            array->child->prev = item;
        }
    }

    return true;
}

/*  新增cJSON节点核心方法
    功能：处理待插入节点key值和type
    object: 被插入父节点
    string: 键值
    item:   待插入节点
    hooks:  内存钩子
    constant_key: 
*/
static cJSON_bool add_item_to_object(cJSON * const object, const char * const string, cJSON * const item, const internal_hooks * const hooks, const cJSON_bool constant_key)
{
    char *new_key = NULL;
    int new_type = cJSON_Invalid;

    if ((object == NULL) || (string == NULL) || (item == NULL) || (object == item))
    {
        return false;
    }

    if (constant_key)
    {
        new_key = (char*)cast_away_const(string);
        new_type = item->type | cJSON_StringIsConst;
    }
    else
    {
        new_key = (char*)cJSON_strdup((const unsigned char*)string, hooks);
        if (new_key == NULL)
        {
            return false;
        }

        new_type = item->type & ~cJSON_StringIsConst;
    }

    if (!(item->type & cJSON_StringIsConst) && (item->string != NULL))
    {
        hooks->deallocate(item->string);
    }

    item->string = new_key;
    item->type = new_type;

    return add_item_to_array(object, item);
}
// 新增cJSON节点操作
CJSON_PUBLIC(cJSON_bool) cJSON_AddItemToArray(cJSON *array, cJSON *item)
{
    return add_item_to_array(array, item);
}
CJSON_PUBLIC(cJSON_bool) cJSON_AddItemToObject(cJSON *object, const char *string, cJSON *item)
{
    return add_item_to_object(object, string, item, &global_hooks, false);
}
CJSON_PUBLIC(cJSON_bool) cJSON_AddItemToObjectCS(cJSON *object, const char *string, cJSON *item)
{
    return add_item_to_object(object, string, item, &global_hooks, true);
}
CJSON_PUBLIC(cJSON_bool) cJSON_AddItemReferenceToArray(cJSON *array, cJSON *item)
{
    if (array == NULL)
    {
        return false;
    }

    return add_item_to_array(array, create_reference(item, &global_hooks));
}
CJSON_PUBLIC(cJSON_bool) cJSON_AddItemReferenceToObject(cJSON *object, const char *string, cJSON *item)
{
    if ((object == NULL) || (string == NULL))
    {
        return false;
    }

    return add_item_to_object(object, string, create_reference(item, &global_hooks), &global_hooks, false);
}
CJSON_PUBLIC(cJSON*) cJSON_AddNullToObject(cJSON * const object, const char * const name)
{
    cJSON *null = cJSON_CreateNull();
    if (add_item_to_object(object, name, null, &global_hooks, false))
    {
        return null;
    }

    cJSON_Delete(null);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddTrueToObject(cJSON * const object, const char * const name)
{
    cJSON *true_item = cJSON_CreateTrue();
    if (add_item_to_object(object, name, true_item, &global_hooks, false))
    {
        return true_item;
    }

    cJSON_Delete(true_item);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddFalseToObject(cJSON * const object, const char * const name)
{
    cJSON *false_item = cJSON_CreateFalse();
    if (add_item_to_object(object, name, false_item, &global_hooks, false))
    {
        return false_item;
    }

    cJSON_Delete(false_item);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddBoolToObject(cJSON * const object, const char * const name, const cJSON_bool boolean)
{
    cJSON *bool_item = cJSON_CreateBool(boolean);
    if (add_item_to_object(object, name, bool_item, &global_hooks, false))
    {
        return bool_item;
    }

    cJSON_Delete(bool_item);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddNumberToObject(cJSON * const object, const char * const name, const double number)
{
    cJSON *number_item = cJSON_CreateNumber(number);
    if (add_item_to_object(object, name, number_item, &global_hooks, false))
    {
        return number_item;
    }

    cJSON_Delete(number_item);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddStringToObject(cJSON * const object, const char * const name, const char * const string)
{
    cJSON *string_item = cJSON_CreateString(string);
    if (add_item_to_object(object, name, string_item, &global_hooks, false))
    {
        return string_item;
    }

    cJSON_Delete(string_item);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddRawToObject(cJSON * const object, const char * const name, const char * const raw)
{
    cJSON *raw_item = cJSON_CreateRaw(raw);
    if (add_item_to_object(object, name, raw_item, &global_hooks, false))
    {
        return raw_item;
    }

    cJSON_Delete(raw_item);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddObjectToObject(cJSON * const object, const char * const name)
{
    cJSON *object_item = cJSON_CreateObject();
    if (add_item_to_object(object, name, object_item, &global_hooks, false))
    {
        return object_item;
    }

    cJSON_Delete(object_item);
    return NULL;
}
CJSON_PUBLIC(cJSON*) cJSON_AddArrayToObject(cJSON * const object, const char * const name)
{
    cJSON *array = cJSON_CreateArray();
    if (add_item_to_object(object, name, array, &global_hooks, false))
    {
        return array;
    }

    cJSON_Delete(array);
    return NULL;
}

// 删除cJSON节点操作
CJSON_PUBLIC(cJSON *) cJSON_DetachItemViaPointer(cJSON *parent, cJSON * const item)
{
    if ((parent == NULL) || (item == NULL))
    {
        return NULL;
    }

    // 删除节点不是头尾节点
    if (item != parent->child)
    {
        /* not the first element */
        item->prev->next = item->next;
    }
    if (item->next != NULL)
    {
        /* not the last element */
        item->next->prev = item->prev;
    }

    // 处理待删除节点为头尾节点时的特殊操作
    if (item == parent->child)
    {
        /* first element */
        parent->child = item->next;
    }
    else if (item->next == NULL)
    {
        /* last element */
        parent->child->prev = item->prev;
    }

    /* 断开节点的所有链接 */
    item->prev = NULL;
    item->next = NULL;

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_DetachItemFromArray(cJSON *array, int which)
{
    if (which < 0)
    {
        return NULL;
    }

    return cJSON_DetachItemViaPointer(array, get_array_item(array, (size_t)which));
}
CJSON_PUBLIC(void) cJSON_DeleteItemFromArray(cJSON *array, int which)
{
    cJSON_Delete(cJSON_DetachItemFromArray(array, which));
}
CJSON_PUBLIC(cJSON *) cJSON_DetachItemFromObject(cJSON *object, const char *string)
{
    cJSON *to_detach = cJSON_GetObjectItem(object, string);

    return cJSON_DetachItemViaPointer(object, to_detach);
}
CJSON_PUBLIC(cJSON *) cJSON_DetachItemFromObjectCaseSensitive(cJSON *object, const char *string)
{
    cJSON *to_detach = cJSON_GetObjectItemCaseSensitive(object, string);

    return cJSON_DetachItemViaPointer(object, to_detach);
}
CJSON_PUBLIC(void) cJSON_DeleteItemFromObject(cJSON *object, const char *string)
{
    cJSON_Delete(cJSON_DetachItemFromObject(object, string));
}
CJSON_PUBLIC(void) cJSON_DeleteItemFromObjectCaseSensitive(cJSON *object, const char *string)
{
    cJSON_Delete(cJSON_DetachItemFromObjectCaseSensitive(object, string));
}

// 指定数组位置插入，insert: which代表位置  array是待插入数组
CJSON_PUBLIC(cJSON_bool) cJSON_InsertItemInArray(cJSON *array, int which, cJSON *newitem)
{
    cJSON *after_inserted = NULL;

    if (which < 0)
    {
        return false;
    }

    after_inserted = get_array_item(array, (size_t)which);
    if (after_inserted == NULL)
    {
        // 插入位置为末端，直接追加即可
        return add_item_to_array(array, newitem);
    }

    // 双链表链接
    newitem->next = after_inserted;
    newitem->prev = after_inserted->prev;
    after_inserted->prev = newitem;
    // 首部插入，则需替换父节点指向
    if (after_inserted == array->child)
    {
        array->child = newitem;
    }
    else
    {
        newitem->prev->next = newitem;
    }
    return true;
}

// 替换操作第三步，核心链表操作。 parent: 原节点父节点，item: 原节点（待替换节点），replacement: 目标节点
CJSON_PUBLIC(cJSON_bool) cJSON_ReplaceItemViaPointer(cJSON * const parent, cJSON * const item, cJSON * replacement)
{
    if ((parent == NULL) || (replacement == NULL) || (item == NULL))
    {
        return false;
    }

    if (replacement == item)
    {
        return true;
    }

    // 1.链接新节点前驱和后继
    replacement->next = item->next;
    replacement->prev = item->prev;
    // 2.处理后继节点的前驱
    if (replacement->next != NULL)
    {
        replacement->next->prev = replacement;
    }
    // 3.处理前驱节点的后继（头结点和非头节点不同处理）
    if (parent->child == item)
    {
        // item是头结点，且链表中只有一个节点，则需修改prev，因为刚刚指向了item->prev，且无前驱节点
        if (parent->child->prev == parent->child)
        {
            replacement->prev = replacement;
        }
        parent->child = replacement;
    }
    else
    {   /*
         * To find the last item in array quickly, we use prev in array.
         * We can't modify the last item's next pointer where this item was the parent's child
         */
        if (replacement->prev != NULL)
        {
            replacement->prev->next = replacement;
        }
        // 替换位置是尾部
        if (replacement->next == NULL)
        {
            parent->child->prev = replacement;
        }
    }

    // 释放替换下来的节点
    item->next = NULL;
    item->prev = NULL;
    cJSON_Delete(item);

    return true;
}
// 替换节点第二步，修改新节点key值为string，根据string查找替换位置节点
static cJSON_bool replace_item_in_object(cJSON *object, const char *string, cJSON *replacement, cJSON_bool case_sensitive)
{
    if ((replacement == NULL) || (string == NULL))
    {
        return false;
    }

    /* replace the name in the replacement */
    if (!(replacement->type & cJSON_StringIsConst) && (replacement->string != NULL))
    {
        cJSON_free(replacement->string);
    }
    replacement->string = (char*)cJSON_strdup((const unsigned char*)string, &global_hooks);
    if (replacement->string == NULL)
    {
        return false;
    }

    replacement->type &= ~cJSON_StringIsConst;

    return cJSON_ReplaceItemViaPointer(object, get_object_item(object, string, case_sensitive), replacement);
}
// 替换节点第一步，key不区分字符大小写
CJSON_PUBLIC(cJSON_bool) cJSON_ReplaceItemInObject(cJSON *object, const char *string, cJSON *newitem)
{
    return replace_item_in_object(object, string, newitem, false);
}
// 替换节点第一步，key区分字符大小写
CJSON_PUBLIC(cJSON_bool) cJSON_ReplaceItemInObjectCaseSensitive(cJSON *object, const char *string, cJSON *newitem)
{
    return replace_item_in_object(object, string, newitem, true);
}
// 指定数组索引替换
CJSON_PUBLIC(cJSON_bool) cJSON_ReplaceItemInArray(cJSON *array, int which, cJSON *newitem)
{
    if (which < 0)
    {
        return false;
    }

    return cJSON_ReplaceItemViaPointer(array, get_array_item(array, (size_t)which), newitem);
}

// 创建cJSON节点
CJSON_PUBLIC(cJSON *) cJSON_CreateNull(void)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        item->type = cJSON_NULL;
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateTrue(void)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        item->type = cJSON_True;
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateFalse(void)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        item->type = cJSON_False;
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateBool(cJSON_bool boolean)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        // 0是false，非0都是true
        item->type = boolean ? cJSON_True : cJSON_False;
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateNumber(double num)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        item->type = cJSON_Number;
        item->valuedouble = num;

        /* use saturation in case of overflow */
        // 为什么要设置valueint？
        if (num >= INT_MAX)
        {
            item->valueint = INT_MAX;
        }
        // 为什么要强转
        else if (num <= (double)INT_MIN)
        {
            item->valueint = INT_MIN;
        }
        else
        {
            item->valueint = (int)num;
        }
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateString(const char *string)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        item->type = cJSON_String;
        item->valuestring = (char*)cJSON_strdup((const unsigned char*)string, &global_hooks);
        if(!item->valuestring)
        {
            cJSON_Delete(item);
            return NULL;
        }
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateStringReference(const char *string)
{
    // 创建字符引用类型，无法通过cJSON_Delete释放该引用
    cJSON *item = cJSON_New_Item(&global_hooks);
    if (item != NULL)
    {
        // 双类型：cJSON_String+cJSON_IsReference
        item->type = cJSON_String | cJSON_IsReference;
        item->valuestring = (char*)cast_away_const(string);
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateObjectReference(const cJSON *child)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if (item != NULL) {
        item->type = cJSON_Object | cJSON_IsReference;
        item->child = (cJSON*)cast_away_const(child);
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateArrayReference(const cJSON *child) {
    cJSON *item = cJSON_New_Item(&global_hooks);
    if (item != NULL) {
        item->type = cJSON_Array | cJSON_IsReference;
        item->child = (cJSON*)cast_away_const(child);
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateRaw(const char *raw)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        item->type = cJSON_Raw;
        item->valuestring = (char*)cJSON_strdup((const unsigned char*)raw, &global_hooks);
        if(!item->valuestring)
        {
            cJSON_Delete(item);
            return NULL;
        }
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateObject(void)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if (item)
    {
        item->type = cJSON_Object;
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateArray(void)
{
    cJSON *item = cJSON_New_Item(&global_hooks);
    if(item)
    {
        item->type=cJSON_Array;
    }

    return item;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateIntArray(const int *numbers, int count)
{
    size_t i = 0;
    cJSON *n = NULL;
    cJSON *p = NULL;
    cJSON *a = NULL;

    if ((count < 0) || (numbers == NULL))
    {
        return NULL;
    }

    a = cJSON_CreateArray();

    for(i = 0; a && (i < (size_t)count); i++)
    {
        n = cJSON_CreateNumber(numbers[i]);
        // 保持原子性，一个元素出错，直接回滚删除，返回NULL
        if (!n)
        {
            cJSON_Delete(a);
            return NULL;
        }
        if(!i)
        {
            // 数组首个结点是顶级节点的子节点
            a->child = n;
        }
        else
        {
            // 非首个节点，即为前驱节点的同级节点（双链表链接）
            suffix_object(p, n);
        }
        // 节点后移
        p = n;
    }

    // 数组首节点前驱链接  考虑添加尾结点后继链接：n->next = a->child;
    if (a && a->child) {
        a->child->prev = n;
    }

    return a;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateFloatArray(const float *numbers, int count)
{
    size_t i = 0;
    cJSON *n = NULL;
    cJSON *p = NULL;
    cJSON *a = NULL;

    if ((count < 0) || (numbers == NULL))
    {
        return NULL;
    }

    a = cJSON_CreateArray();

    for(i = 0; a && (i < (size_t)count); i++)
    {
        n = cJSON_CreateNumber((double)numbers[i]);
        if(!n)
        {
            cJSON_Delete(a);
            return NULL;
        }
        if(!i)
        {
            a->child = n;
        }
        else
        {
            suffix_object(p, n);
        }
        p = n;
    }

    if (a && a->child) {
        a->child->prev = n;
    }

    return a;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateDoubleArray(const double *numbers, int count)
{
    size_t i = 0;
    cJSON *n = NULL;
    cJSON *p = NULL;
    cJSON *a = NULL;

    if ((count < 0) || (numbers == NULL))
    {
        return NULL;
    }

    a = cJSON_CreateArray();

    for(i = 0; a && (i < (size_t)count); i++)
    {
        n = cJSON_CreateNumber(numbers[i]);
        if(!n)
        {
            cJSON_Delete(a);
            return NULL;
        }
        if(!i)
        {
            a->child = n;
        }
        else
        {
            suffix_object(p, n);
        }
        p = n;
    }

    if (a && a->child) {
        a->child->prev = n;
    }

    return a;
}
CJSON_PUBLIC(cJSON *) cJSON_CreateStringArray(const char *const *strings, int count)
{
    size_t i = 0;
    cJSON *n = NULL;
    cJSON *p = NULL;
    cJSON *a = NULL;

    if ((count < 0) || (strings == NULL))
    {
        return NULL;
    }

    a = cJSON_CreateArray();

    for (i = 0; a && (i < (size_t)count); i++)
    {
        n = cJSON_CreateString(strings[i]);
        if(!n)
        {
            cJSON_Delete(a);
            return NULL;
        }
        if(!i)
        {
            a->child = n;
        }
        else
        {
            suffix_object(p,n);
        }
        p = n;
    }

    if (a && a->child) {
        a->child->prev = n;
    }

    return a;
}

// 复制， 浅copy和深copy recurse==true:深
CJSON_PUBLIC(cJSON *) cJSON_Duplicate(const cJSON *item, cJSON_bool recurse)
{
    cJSON *newitem = NULL;
    cJSON *child = NULL;
    cJSON *next = NULL;
    cJSON *newchild = NULL;

    /* Bail on bad ptr */
    if (!item)
    {
        goto fail;
    }
    /* Create new item */
    newitem = cJSON_New_Item(&global_hooks);
    if (!newitem)
    {
        goto fail;
    }
    /* Copy over all vars */
    newitem->type = item->type & (~cJSON_IsReference);
    newitem->valueint = item->valueint;
    newitem->valuedouble = item->valuedouble;
    if (item->valuestring)
    {
        newitem->valuestring = (char*)cJSON_strdup((unsigned char*)item->valuestring, &global_hooks);
        if (!newitem->valuestring)
        {
            goto fail;
        }
    }
    if (item->string)
    {
        newitem->string = (item->type&cJSON_StringIsConst) ? item->string : (char*)cJSON_strdup((unsigned char*)item->string, &global_hooks);
        if (!newitem->string)
        {
            goto fail;
        }
    }

    /* If non-recursive, then we're done!  非递归复制*/
    if (!recurse)
    {
        return newitem;
    }

    /* Walk the ->next chain for the child. 递归复制*/
    child = item->child;
    while (child != NULL)
    {
        /* Duplicate (with recurse) each item in the ->next chain  next用于辅助单链表链接 */
        newchild = cJSON_Duplicate(child, true); 
        if (!newchild)
        {
            goto fail;
        }
        if (next != NULL)
        {
            /* If newitem->child already set, then crosswire ->prev and ->next and move on */
            next->next = newchild;
            newchild->prev = next;
            next = newchild;
        }
        else
        {
            /* Set newitem->child and move to it */
            newitem->child = newchild;
            next = newchild;
        }
        child = child->next;
    }
    if (newitem && newitem->child)
    {
        newitem->child->prev = newchild;
    }

    return newitem;

fail:  // 处理失败，则需释放构建的newitem的空间
    if (newitem != NULL)
    {
        cJSON_Delete(newitem);
    }

    return NULL;
}

// 查找字符串下一个'\n'，去除字符串中的单行注释
static void skip_oneline_comment(char **input)
{
    *input += static_strlen("//");

    for (; (*input)[0] != '\0'; ++(*input))
    {
        if ((*input)[0] == '\n') {
            *input += static_strlen("\n");
            return;
        }
    }
}
// 查找字符串下一个'*/'，去除字符串中的块注释
static void skip_multiline_comment(char **input)
{
    *input += static_strlen("/*");

    for (; (*input)[0] != '\0'; ++(*input))
    {
        if (((*input)[0] == '*') && ((*input)[1] == '/'))
        {
            *input += static_strlen("*/");
            return;
        }
    }
}
// 提取input中最小字符串至output
static void minify_string(char **input, char **output) {
    (*output)[0] = (*input)[0];
    *input += static_strlen("\"");
    *output += static_strlen("\"");

    for (; (*input)[0] != '\0'; (void)++(*input), ++(*output)) {
        (*output)[0] = (*input)[0];

        if ((*input)[0] == '\"') {
            (*output)[0] = '\"';
            *input += static_strlen("\"");
            *output += static_strlen("\"");
            return;
        } else if (((*input)[0] == '\\') && ((*input)[1] == '\"')) {
            (*output)[1] = (*input)[1];
            *input += static_strlen("\"");
            *output += static_strlen("\"");
        }
    }
}

// 压缩字符串，删除JSON节点间的空白符
CJSON_PUBLIC(void) cJSON_Minify(char *json)
{
    char *into = json;

    if (json == NULL)
    {
        return;
    }

    // 遍历整字符数组（即字符串），json可理解为游标指针
    while (json[0] != '\0')
    {
        switch (json[0])
        {
            case ' ':
            case '\t':
            case '\r':
            case '\n':
                json++;
                break;
            // 去除字符串中的注释
            case '/':
                if (json[1] == '/')
                {
                    skip_oneline_comment(&json);
                }
                else if (json[1] == '*')
                {
                    skip_multiline_comment(&json);
                } else {
                    json++;
                }
                break;
            // 搜索至字符串
            case '\"':
                minify_string(&json, (char**)&into);
                break;
            default:
                into[0] = json[0];
                json++;
                into++;
        }
    }
    // 结尾符
    *into = '\0';
}

// 节点数据类型判断
CJSON_PUBLIC(cJSON_bool) cJSON_IsInvalid(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_Invalid;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsFalse(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_False;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsTrue(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xff) == cJSON_True;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsBool(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & (cJSON_True | cJSON_False)) != 0;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsNull(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_NULL;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsNumber(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_Number;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsString(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_String;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsArray(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_Array;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsObject(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_Object;
}
CJSON_PUBLIC(cJSON_bool) cJSON_IsRaw(const cJSON * const item)
{
    if (item == NULL)
    {
        return false;
    }

    return (item->type & 0xFF) == cJSON_Raw;
}

// 比较cJSON节点
CJSON_PUBLIC(cJSON_bool) cJSON_Compare(const cJSON * const a, const cJSON * const b, const cJSON_bool case_sensitive)
{
    // 至少有一个节点为NULL，或者节点类型不相等，则返回false
    if ((a == NULL) || (b == NULL) || ((a->type & 0xFF) != (b->type & 0xFF)))
    {
        return false;
    }

    /* check if type is valid */
    /* switch 只要满足一个case就会执行下面所有case语句*/
    switch (a->type & 0xFF)
    {
        case cJSON_False:
        case cJSON_True:
        case cJSON_NULL:
        case cJSON_Number:
        case cJSON_String:
        case cJSON_Raw:
        case cJSON_Array:
        case cJSON_Object:
            break;

        default:
            return false;
    }

    /* identical objects are equal */
    /* 引用相等*/
    if (a == b)
    {
        return true;
    }

    switch (a->type & 0xFF)
    {
        /* in these cases and equal type is enough */
        case cJSON_False:
        case cJSON_True:
        case cJSON_NULL:
            return true;

        case cJSON_Number:
            if (compare_double(a->valuedouble, b->valuedouble))
            {
                return true;
            }
            return false;

        case cJSON_String:
        case cJSON_Raw:
            if ((a->valuestring == NULL) || (b->valuestring == NULL))
            {
                return false;
            }
            if (strcmp(a->valuestring, b->valuestring) == 0)
            {
                return true;
            }

            return false;

        case cJSON_Array:
        {
            cJSON *a_element = a->child;
            cJSON *b_element = b->child;

            for (; (a_element != NULL) && (b_element != NULL);)
            {
                if (!cJSON_Compare(a_element, b_element, case_sensitive))
                {
                    return false;
                }

                a_element = a_element->next;
                b_element = b_element->next;
            }

            /* one of the arrays is longer than the other */
            if (a_element != b_element) {
                return false;
            }

            return true;
        }

        case cJSON_Object:
        {
            cJSON *a_element = NULL;
            cJSON *b_element = NULL;
            cJSON_ArrayForEach(a_element, a)
            {
                /* TODO This has O(n^2) runtime, which is horrible! */
                b_element = get_object_item(b, a_element->string, case_sensitive);
                if (b_element == NULL)
                {
                    return false;
                }

                if (!cJSON_Compare(a_element, b_element, case_sensitive))
                {
                    return false;
                }
            }

            /* doing this twice, once on a and b to prevent true comparison if a subset of b
             * TODO: Do this the proper way, this is just a fix for now */
            cJSON_ArrayForEach(b_element, b)
            {
                a_element = get_object_item(a, b_element->string, case_sensitive);
                if (a_element == NULL)
                {
                    return false;
                }

                if (!cJSON_Compare(b_element, a_element, case_sensitive))
                {
                    return false;
                }
            }

            return true;
        }

        default:
            return false;
    }
}

// 存储空间操作
CJSON_PUBLIC(void *) cJSON_malloc(size_t size)
{
    return global_hooks.allocate(size);
}
CJSON_PUBLIC(void) cJSON_free(void *object)
{
    global_hooks.deallocate(object);
}